de:Entzug ja:引きこもり When an addictive behavior is stopped or an addictive substance is withdrawn from use, withdrawal symptoms almost always follow. Depending on the behavior or substance, these symptoms can appear within a few hours (nicotine) or over a few days or weeks (alcohol, or most behavioral addictions). (Note that the following descriptions apply to both substances and behaviors.)

Symptoms themselves vary significantly from addiction to addiction, but there are some commonalities. Withdrawal from addictive substances is typically followed by anxiety and craving, while behavioral withdrawal is marked by a need to continue the behavior despite reason or logic.

Withdrawal symptoms may vary from individual to individual for the same substance. Some people are able to quit smoking "cold turkey," (i.e. immediately, without any tapering off), while others may never find success despite repeated efforts. The length of time and the degree to which an addict has been involved with a substance is also an indicator of the severity of withdrawal.

Withdrawal is a more serious medical issue for some substances than for others. While nicotine withdrawal, for instance, is usually managed without medical intervention, attempting to give up a benzodiazepine or alcohol dependency can result in seizures if not carried out properly.

One of the primary agents in withdrawal is the brain chemical dopamine. When humans engage in a pleasurable activity, one physiological reaction is the release of dopamine in the brain's pleasure center. Addictive substances such as nicotine and cocaine mimic the class of brain chemicals known as endorphins which regulate the release of dopamine. When the effect of the drug wears off and the dopamine level falls, the user experiences the reduced level as a depressed mood, and will re-use in order to re-establish, quite literally, a "high."

An interesting side-note is that abstention from some substances which are generally considered highly addictive may not result in withdrawal. There exist documented cases of soldiers returning from Vietnam with heroin addictions. Once home, with the pressure of war behind them, they were able to leave the heroin behind as well (see Rat Park for experiments on rats showing the same results).

Concerns over withdrawal are not limited to substances or activities normally considered addictive. Persons who require antidepressants, for instance, are not addicted to them in the technical sense, yet abrupt, unmonitored withdrawal from such medications is potentially lethal as a result of the emotional state it can precipitate.